Sound amplifier



J21111- 21, 1941- c.' R. LA MAR ETAL 2,229,296

SOUND AMPLIFIER Filed Nov. 12, 1938 3 I/V VIS/V TORi CMR/.Es R. La /V/m.

Patented Jan. 21, 1941 PATENT OFFICE SOUND ABHLIFIER Charles Roy La Mar and Leland R. Kirby, Long Beach, Calif.

Application November 12, 1938, Serial No. 240,023

5 Claims.

This invention relates to a sound amplier, in which sound is amplified through a mechanism requiring the expenditure of very little power.

An object of our invention is to provide a sound amplifier which will greatly amplify sound passing into a microphone or transmitter, the sound passing out of the loud-speaker being true in tone and without distortion, and the like.

Another object of our invention is to provide a multi-stage sound amplifier, one or more of the stages being capable of being tuned so as to provide the maximum amplification without distortion.

Other objects, advantages and features of invention may appear from the accompanying drawing, the subjoined detailed description and the appended claims.

In the drawing- Figure 1 is a wiring diagram of our sound amplier.

Figure 2 is a transverse, sectional view of the first stage of amplication.

Figure 3 is a transverse sectional view of the second stage 0f amplication.

Figure 4 is a fragmentary, Vertical, sectional view of the tube forming a part of the second amplifier.

Figure 5 is a top plan View of the second amplier.

Referring more particularly to the drawing, the numeral I indicates a microphone or transmitter into which sound passes from the source requiring amplification. Ihe rst stage of amplification 2 includes an electromagnet 3, mounted in a housing 4. One end of the windings of the electromagnet 3 is wired to a battery 5, and thence back to the microphone I. The other end of the windings of the electromagnet 3 is electrically connected to an adjustable rheostat 6, and thence to the microphone I. A diaphragm I is mounted in the housing 4 immediately above the electromagnet 3, and this diaphragm is actuated by the electromagnet 3.

A transmitting button 8 is mounted above the diaphragm 'I, and this button is preferably of the usual and well-known granular carbon type. The disk 9 of the transmitter is xedly attached to the diaphragm 'I by means of the pin I0. A second amplier II comprises a housing I2, which encloses an electromagnet I3. A battery I4 is electrically connected to one end of the coils of the electromagnetl3, and the other end of the battery is connected through a variable rheostat I5, and thence back to the other end of the Windings of the electromagnet I3.

tery 20, and thence to the other end o1 the 10 coil I8.

A horizontal tube 2| is mounted on the upper end of the housing I2. The tube 2| contains a wire 22, which extends longitudinally of the tube,

and is stretched taut by means of plugs 23, 15

which screw into the end of the tube. By adjusting the plugs 23 the tone of the wire 22 can be changed as desired or necessary. A transmitting button 24 of the granular carbon type is slidably or adjustably mounted on the tube 2|. 'I'he 20 cap I'I has a pin 25 rising therefrom, and this pin is xedly attached to the Wire 22.

The disk 26 of the button 24 is provided with a pin 21, which slidably engages the wire 22. The pin 21 extends through a slot 28 in the top of the tube ZI, thus enabling the button 24 to be adjusted longitudinally of the wire 22 for the purpose of engaging the wire at points of maximum or minimum vibration or intermediate points as may be desired or necessary. Maximum amplification in the second unit will be obtained when the button 24 is so adjusted that the pin 21 will engage the wire 22 at a point of maximum vibration. To eliminate overtones 3 or other objectionable noises, the button 24 might be adjusted to some point other than the point of maximum amplication. A loud-speaker 29 of usual and Well-known construction is electrically connected to the transmitter button 24, and a variable rheostat 30 included in the loudspeaker circuit controls the amount of current fed into a loud-speaker from the button 24.

In operation, the microphone I picks up the sound which is to be amplified, the electromagnet 3 is then actuated, and the diaphragm I will vibrate to create the first stage of amplification. The carbon transmitter 8 then picks up the amplified sound and transmits it to the coil I8, the current of which is supplied by the battery 20. The wire 22 is then caused to vibrate as soon as it is directly connected to the cap II, which rests on the coil I6. The transmitter 24 then picks up the amplified sound from the wire 22, and transmits this amplified sound to the loud-speaker 29 where it is again amplified in the usual and well-known manner of a power speaker.

Having described our invention, we claim:

1. A sound amplier unit comprising a housing, a tautly stretched wire mounted in the housing, an electromagnet means adjacent the wire, a core in the electromagnet means, means positively connecting the core and the wire whereby a vibration is imparted to the wire from the core, a transmitter adjustably mounted on the housing, and means extending from the transmitter and adjustably engaging said Wire.

2. A sound amplifier unit, comprising a housing, an electromagnet in the housing, a core in the electromagnet, a tautly stretched wire inthe housing, a cap on the core, a coil surrounding the cap, means positively connecting the cap and the wire, a transmitter mounted on the housing, and means depending from the transmitter and adjustably engaging said wire.

3. A sound amplier unit comprising a housing, a tautly stretched wire mounted in the housing, an electromagnet means adjacent the wire, a'core in the electromagnet means, means positively connecting the core andthe wire whereby a Vibration is imparted to the wire from the core, a transmitter adjustably mounted on the housing, means extending from the transmitter and adjustably engaging said wire, said transmitter being slidably mounted on the housing, and adjustable relative to said wire.

4. A sound amplifier unit comprising a housing, an electromagnet in the housing, a core in the electromagnet, a tautly stretched wire in the housing, a cap on the core, a coil surrounding the cap, means positively connecting the cap and the wire, a transmitter mounted on the housing, means depending from the transmitter and adjustably engaging said wire, said transmitter being slidably mounted on the housing, and adjustable relative to said wire.

5. A sound amplifier unit comprising a housing, a tautly stretched wire mounted in the housing, an electromagnet means adjacent the wire, a core in the electromagnet means, a pin xedly attached to the stretched wire and operatively attached to the core whereby a vibration is imparted to the wire from the core, a transmitter adjustably mounted on the housing, a second pin extending from the transmitter and slidably engaging said Wire.

CHARLES ROY LA MAR. LELAND R. KlRBY. 

